1. Field of the Invention
The invention relates to a driving device. Particularly, the invention relates to a light emitting diode (LED) driving device and a driving method thereof.
2. Description of Related Art
Since a liquid crystal display (LCD) has advantages of lightness, thinness, shortness, smallness, low power consumption and no irradiation, it is widely applied in portable electronic devices such as personal digital assistants (PDAs), notebooks (NBs) and digital cameras. Since a LCD panel of the LCD cannot emit light itself, a backlight module has to be disposed under the LCD panel to provide a light source, so as to achieve a display function. Moreover, in order to achieve a light and thin effect, the portable electronic device generally uses a light emitting diode (LED) as the light source of the backlight module.
When the portable electronic device uses commercial power as a power supply, the backlight module can provide a brighter light source to improve a display effect of the portable electronic device without power problem. Conversely, when the portable electronic device uses a battery as the power supply, in order to ensure a longer usage time of the portable electronic device, brightness of the backlight module thereof is reduced to reduce the power consumption. Generally, adjustment of the brightness of the backlight module can be implemented by adjusting a duty cycle of a driving signal. In other words, if the duty cycle of the driving signal is 100% when the portable electronic device uses the commercial power, the duty cycle of the driving signal is 50% when the portable electronic device uses the battery. In this way, power consumption of the portable electronic device using the battery is reduced, and the usage time of the portable electronic device is prolonged.